The fourth species of Sinamma Lin & Li, 2014 (Araneae, Tetrablemmidae) from China

Abstract Background Sinamma Lin & Li, 2014 is a small tetrablemmid genus distributed in China, with three currently known species: Sinammaoxycera Lin & Li, 2014 from Guangxi Zhuang Autonomous Region and S.quadrata Tong & Li, 2022 and S.yingae Tong & Li, 2022 from Guangdong Province. New information While examining spider specimens obtained by sifting leaf litter from Danxiashan National Nature Reserve in Guangdong Province of China, we discovered a new species of the genus Sinamma, S.danxia sp. nov., which is described here.


Introduction
Members of Tetrablemmidae O. Pickard-Cambridge, 1873, commonly known as tetrablemmid armoured spiders, are very small (< 2 mm length) haplogyne spiders, which can easily be recognised by their strap-like abdominal scuta arranged in parallel (Brescovit and Cizauskas 2019).The family currently comprises 151 species in 27 genera, distributed in southern Asia, Africa and Central and South America (WSC 2024), where they are found in leaf litter, soil and in caves (Burger et al. 2010).Lin and Li (2014) established the genus Sinamma Lin & Li, 2014 based on the type species S. oxycera Lin & Li, 2014 from Guangxi, China and transferred Shearella sanya Lin & Li, 2010 to it, based on some less diagnostic characteristics, such as the pointed eye tubercle, the moderately modified male leg I and the subjectively perceived narrow postgenital plate in the female.Subsequently, Sankaran and Sebastian (2016) transferred Sinamma sanya (Lin and Li 2010) back to Shearella.Later, Cheng et al. (2022) described two more Sinamma species (S. quadrata Tong &Li, 2022 andS. yingae Tong &Li, 2022) from Guangdong, China.To date, three species of this genus have been reported, all distributed in southern China.
In this paper, the fourth species of the genus, Sinamma from south China, is described as S. danxia sp.nov.

Materials and methods
All measurements are given in millimetres (mm).Leg measurements are shown as total length (femur, patella, tibia, metatarsus, tarsus).Vulva was cleared in pancreatin solution (Álvarez-Padilla and Hormiga 2007).All specimens are preserved in 75% alcohol.Photographs were taken using an Olympus BX53 microscope equipped with a Kuy Nice CCD camera and were imported into Helicon Focus v. 7 for stacking.Final figures were retouched by the Adobe Photoshop © 2020.The type specimens of the new species are deposited in the School of Biology and Agriculture, Shaoguan University, Shaoguan, China.
Terms and abbreviations used in the text and figures follow Cheng et al. (2022).
Palp (Fig. 3D-F Carapace (Fig. 1D, F, C and D): cephalic part raised, dorsal edge straight in lateral view (Fig. 2D), ocular area not raised, clypeus lower than in male; cheliceral horn absent.Legs as in male, except for leg I not swollen.

Diagnosis
Amongst the congeners, the new species can be easily distinguished from S. oxycera and S. quadrata by the presence of pointed cephalic tubercles in the latter two species (both sexes in S. oxycera and males in S. quadrata).The new species is similar to S. yingae Tong & Li, 2022 in that both males and females lack pointed cephalic tubercles and in the pattern of leg tubercles on tibia and metatarsus I, but can be recognised by: Cheng et al. ( 2022); 1) dorsal surface of the cephalic part in females straight in lateral view (D) (vs.cephalic part slightly sloping (Cheng et al. (2022): fig.5F)); 2) metatarsus I without proximal tubercle (Fig. 3B and C) (vs.metatarsus I with one proximal tubercle (Cheng et al. (2022): fig.3D)); 3) the length of the male palpal patella about 1/2 of the femur in length (Fig. 3D and E) (vs. the patella about 2/3 femur in length (Cheng et al. (2022): figs.6A and B)); 4) embolus bending at a nearly right angle at base (Fig. 3D and E  The fourth species of Sinamma Lin &amp; Li, 2014 (Araneae, Tetrablemmidae) ...

Etymology
The specific epithet refers to the type locality; noun in apposition.

Distribution
Known only from the type locality (Guangdong, China) (Fig. 5)

Figure 5 .
Figure 5. Map showing the currently known localities of Sinamma spp.
): femur smooth, slightly curved at mid-ventral side; patella approximately 1/2 of femur in length, connected to tibia sub-basally; bulb long, pyriform, with a distinct contraction in middle of ventral surface; embolus long, spiniform, strongly sclerotised and bending at a nearly right angle at base towards dorsally; sperm duct extending, visible through the bulbal integument.